Defects and Properties of Cast Metals IV: Defects I - Molten Metal and Inclusions
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Solidification Committee
Program Organizers: Lang Yuan, University of South Carolina; Brian Thomas, Colorado School of Mines; Peter Lee, University College London; Mark Jolly, Cranfield University; Alex Plotkowski, Oak Ridge National Laboratory; Andrew Kao, University of Greenwich; Kyle Fezi, Fort Wayne Metals
Monday 8:30 AM
February 28, 2022
Room: 210B
Location: Anaheim Convention Center
Session Chair: Brian Thomas, Colorado School of Mines; Mark Jolly, Cranfield University
8:30 AM Introductory Comments
8:35 AM Invited
Measurement and Simulation of Reoxidation Inclusions in Steel Casting: Robert Donahue1; Christoph Beckermann1; 1University of Iowa
Reoxidation inclusions that form during mold filling can severely diminish the properties of steel castings and often require costly weld repair. Experiments are performed to measure the volume and distribution of reoxidation inclusions in various casting geometries. The molds are 3D printed and filled with liquid steel using a teapot ladle. The cope surfaces are covered by chill plates to avoid shrinkage cavities and allow for the measurement of all inclusions on the casting surfaces. Flat plates of various inclination angles, blocks with cylindrical cores, and ring castings with dirt traps are investigated. The castings are x-rayed and the inclusion distributions on the surfaces are carefully mapped using image analysis. The experimental results are used to validate a previously developed simulation model that calculates the formation, growth, and buoyant transport of reoxidation inclusions during filling. It is found that the model predicts the measured inclusion distributions well.
9:00 AM
Particle Capture Defects in Continuous Steel Casting: Seong-Mook Cho1; Brian Thomas2; 1Pukyong National University; 2Colorado School of Mines
Many defects such as blisters and slivers in the final steel products manufactured from continuous casting originate from particles captured by the solidifying steel shell in the mold and strand regions. Captured particles include argon gas bubbles injected to prevent nozzle clogging, slag droplets entrained into the molten steel, or non-metallic inclusions from upstream processes. In this work, three-dimensional computational fluid dynamics simulations of transport and capture of particles in the molten steel flow during continuous steel-slab casting are conducted using an advanced capture criterion to simulate entrapment of small particles between the primary dendrite arms and engulfment of large particles by the growing dendrites. The model predictions are validated with plant measurements including ultrasonic testing measurements and step milling measurements. The capture behavior of argon gas bubbles in surface solidification and inclusions in internal solidification are revealed to understand defect formation related to particle capture in continuous steel casting.
9:20 AM
NOW ON-DEMAND ONLY – Understanding Effects of Oxide Bifilms on Solidification Microstructures by Multiscale Modeling: Sepideh Kavousi1; Mohsen Asle Zaeem1; 1Colorado School of Mines
The entrained oxide bifilms in casting of aluminum alloys act as cracks and degrade failure behavior of the products. In this study, a multi-scale computational approach is implemented to investigate how the oxide bifilms affect different stages of solidification of aluminum. Molecular dynamics (MD) is used to investigate if the bifilm surfaces serves as favored sites for heterogenous nucleation. MD results show no significant heterogenous nucleation on the oxide surface during the solidification of undercooled melt. By integrating Navier Stokes equations and phase-field modeling of solidification, we study the interaction between the growing dendrites and oxide bifilms. Based on the MD simulation findings, only formation of homogenous nucleation is considered and columnar to equiaxed transition is studied. This multi-scale model helps to quantify the effect of bifilm size and solidification condition (undercooling temperature, velocity, etc.) on solidification microstructures.
9:40 AM
Characterization of Second Phase Particles in Twin Roll Cast Aluminum Alloy AA 8011: Sooraj Patel1; Jyoti Mukhopadhyay1; 1Indian Institute of Technology Gandhinagar
A thin strip of 7 mm thickness was manufactured using a twin-roll casting process. Second phase particles were segregated at the center region during the solidification of aluminum alloy AA 8011. Such segregations played a vital role in the formation of pinholes. In the present work, the microstructural analysis was carried out to study the centerline segregation. Fine equiaxed grains were formed at the surface due to the rapid solidification and dynamic recrystallization. An increase in hardness was attributed to the centerline segregation of the second phase particles. β-AlFeSi compounds with needle shape morphology were segregated in the thickness range of 10 to 20 µm parallel to the twin-roll casting direction. Sub-grains were formed inside the elongated grains due to dynamic recovery. Dispersoids were precipitated after the homogenization, which was not found in the as-received twin-roll cast strip.